Tree Genetics and Molecular Breeding 2025, Vol.15, No.3, 98-107 http://genbreedpublisher.com/index.php/tgmb 104 colors and better nutrition. This is also of great help in improving the fruit color of Morella rubra and enhancing their quality. 9 Biotechnological Applications and Crop Improvement 9.1 Molecular breeding for enhanced anthocyanin The color of the fruit of Morella rubra is mainly determined by the amount of anthocyanins. Anthocyanins not only make fruits look good in color, but also have high nutritional and health care value. Studies have shown that R2R3-MYB transcription factors, such as MrMYB1 and MrMYB9, are very crucial in the anthocyanin synthesis process, and their expression levels have a strong relationship with anthocyanin accumulation (Niu et al., 2010; Li et al., 2023). By using molecular breeding methods and selecting varieties with high expression levels of MrMYB1, it is possible to breed new varieties with brighter colors and higher nutritional value (Yan et al., 2021). In addition, crops with high anthocyanin content are more tolerant to environmental stresses (such as low temperature and drought), which is very helpful for improving the adaptability of crops (Sun et al., 2021). 9.2 Marker-assisted selection (MAS) and genetic engineering Now, scientists have identified multiple genes related to anthocyanin synthesis, such as MrCHI, MrF3'H, MrANS, MrUFGT, as well as regulatory factors like MrMYB1, MrbHLH1, and MrWD40-1. These genes have all been cloned and functionally verified (Liu et al., 2013b; Li et al., 2023). These genes can be used as molecular markers to help select bayberry varieties with better color more quickly. If genetic engineering, such as transgenic or gene editing techniques, is employed, the expression of these genes can be directly regulated, thereby controlling the amount of anthocyanins. For example, overexpression of MrMYB1 can increase anthocyanins (Niu et al., 2010; Liu et al., 2013a), while inhibiting negative regulatory factors such as MrMYB6 can reduce the decomposition of anthocyanins (Shi et al., 2021). These methods can all be applied to the improvement of fruit color and nutrition (Chaves-Silva et al., 2018; Yan et al., 2021). 9.3 CRISPR/Cas-based genome editing potential New gene editing tools like CRISPR/Cas enable us to precisely modify key genes related to anthocyanins (Han, 2024). By adjusting regulatory factors such as MYB, bHLH, and WD40, or modifying certain structural genes, the entire pathway of anthocyanin synthesis can be optimized, thereby breeding bayberry varieties with better color and higher nutrition (Chaves-Silva et al., 2018; Yan et al., 2021). This technology can also be used to remove negative regulatory factors such as MrMYB6, thereby allowing more anthocyanins to accumulate in the fruit (Shi et al., 2021). The development of these genetic technologies has opened up new ideas for fruit tree breeding and quality improvement in the future. 10 Concluding Remarks In recent years, scientists have made significant progress in the research of genes related to anthocyanin synthesis in Morella rubra. Research has found that there are many transcription factors belonging to the MYB family in Morella rubra. Among them, MrMYB1 and MrMYB9 are R2R3-MYB genes. They are particularly important in regulating anthocyanin synthesis and have a strong relationship with the amount of anthocyanin in the fruit. There are also two important proteins, one called MrbHLH1 and the other MrWD40-1. Together with MYB protein, they form a complex, which can significantly increase the accumulation of anthocyanins. However, there are also some MYB factors, such as MrMYB6, which can have the opposite effect and instead inhibit the synthesis of anthocyanins and proanthocyanidins. These achievements help us better understand how the color of Morella rubra is formed and also lay a foundation for future breeding and nutritional improvement. However, the current understanding of these regulatory genes is still not comprehensive enough. How transcription factors like MYB, bHLH and WD40 interact with each other, what different functions their members have, and how they specifically regulate downstream genes - these questions still require further research. In addition, it is still not very clear how environmental factors such as light and temperature affect anthocyanin synthesis, as well as the relationship between genetic differences and appearance colors among different varieties. Moreover, many functional verifications are currently conducted on other plants. Morella rubra themselves do not yet have a mature transformation system, which also limits further research.
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